A variety of safety restraint systems are known for protecting vehicle occupants during an impact event. Seatbelts and airbags are perhaps the most developed and conventional of known safety systems. Known airbags include those which deploy from the instrument or door panels, vehicle seats, steering wheels, roof rail or headliner areas and other areas of the vehicle.
Knee and lower leg airbag module assemblies have recently been incorporated into an increasing number of vehicles in the industry to enhance occupant responses to select vehicle impact conditions. Still more recent additions to vehicle interior safety restraint systems are deployable semi-rigid expanding restraint volumes, such as a deployable expanding plastic knee bolster bladder having an interior trim panel-like reaction surface that deploys outward from the lower portion of the instrument panel as the bladder expands to contact an occupant and reduce vehicle impact-based occupant injury.
Upon deployment, conventional airbags provide a fabric balloon-like restraint volume enclosure. Restraint systems utilizing semi-rigid expandable restraint volume enclosures commonly expand relatively stiff integral pleat or accordion-like members to provide a generally closed volume, dynamically positioning a relatively firm (but not entirely inflexible) impact reaction surface member for occupant contact. Venting may be provided as well. In the case of one such example of a semi-rigid expandable knee bolster occupant restraint volume enclosure, both the occupant contact surface member and the expanding bladder enclosure are made of relatively statically firm, but dynamically deformable, plastic. Dynamic deformation is necessary to expand and pressurize the bladder-like restraint enclosure volume that provides impact energy management. Known semi-rigid expanding volume enclosure-based occupant restraint devices or systems are comprised of like-material expansion and occupant load contact surface structure members such as plastic, metal, alloy or an alternative stiff material. Such pre-shaped material (molded, formed, etc.) provides a significantly increased static stiffness and may be thicker, compared to that of traditional airbag material for example, while maintaining sufficient expansion member dynamic flexibility to displace the also relatively stiff, but not inflexible, occupant contact surface member and hold a given volumetric shape.
One example recently implemented in automotive vehicles incorporates an injection-molded plastic bladder positioned between inner and outer glove box door panels. Upon impact detection, the bladder is inflated, pushing the semi-rigid (occupant impact-deformable) interior trim-like outer panel straight towards the occupants legs. The impact force is dissipated by the bladder while force is more evenly distributed across the semi-rigid contact panel, compared to the more localized load distribution associated with contact with an airbag cushion. For the referenced application a comparable traditional airbag cushion volume would be substantially greater than that of the expandable injection molded bladder, based on typical available package location options for a deployable cushion located beneath the glove box and instrument panel, airbag cushions further being inherently oversized to permit early contact and ride-down associated with more of a point-loading type occupant interface condition and corresponding local cushion displacement and cushion penetration.
Given that newer semi-rigid expanding restraint volume enclosure devices such as described above follow a more direct route the targeted occupant body contact region over short distances, such restraint systems can be notably smaller and lighter than traditional airbag restraint system counterparts. Additionally, the impact load displacement characteristics of the occupant contact surface member or subassembly that redistributes the force of the impact enables the restraint volume to function effectively with reduced inflation force required, and a correspondingly reduced inflated volume. As a result, a deployment inflator can be substantially smaller than for a traditional airbag, reducing the overall system package mass. For a knee bolster application, an inflator size reduction of 75% has been estimated. A reduced inflator size can further enable package size reduction compared to that of a traditional airbag system.
However, there are challenges associated with deployable semi-rigid expanding restraint volume enclosure implementations incorporating both increased material stiffness occupant contact surface and expanding bladder enclosure support members for implementations requiring further increased inflated volumetric expansion to achieve greater “throw” distances for the occupant contact surface member, compared to that of today's recently implemented semi-rigid expandable restraint volume enclosures. This also applies to semi-rigid expandable plastic restraint volume enclosure devices such as the above-mentioned injection molded knee bolster bladder-based restraint device, for future vehicle applications in a variety of vehicle installed occupant or pedestrian protection locations for which there is a need to fill an increased gap between the deployable semi-rigid expandable restraint volume device and an occupant or pedestrian. These challenges are compounded by extreme temperature challenges stressing plastic material expansion members even further. Significantly increased volume and expansion distances can affect occupant contact surface positional control and result in “hanging mass” effects by adding additional molded pleats.
Further, there are various load carrying stability and deployable occupant contact surface displacement distance limitations associated with the physical A-surface size of a deployable panel-like contact body member as well as the package depth and manufacture-able orientation, depth and quantity of semi-rigid concentric rings or stacked expanding accordion like pleats. Lastly, the semi-rigid deployable bladder-like systems with trim-panel-like occupant or pedestrian impact surfaces are most stable when loaded generally perpendicular to the surface of the contact member, do not provide expansive protective coverage beyond the periphery of the a-surface of the contact panel, currently limiting a variety of vehicle installations
Accordingly, there is a need for a practical and effective advancement of the aforementioned technology to overcome known functional challenges and further enhance vehicle occupant and pedestrian impact protection and injury mitigation capabilities.